Strange leaf discolouration

Over the past couple of days, I've noticed this odd discolouration starting to affect some the young growth at the end of the bines and on the new side shoots. After doing research on some of the hop forums and general Internet searches, it sounds like a nitrogen deficiency, but I'm not sure. It could also be a sign of soil that is too wet. I've left the irrigation system off since the weekend and I'm going to let the soil dry out completely before turning it back on. I'm also going to drill some more holes into the bottom of the pots to ensure adequate drainage.